Masteries

Offense:
22

Defense:
5

Utility:
3

So i did some research on Pantheon and messing around in game to see what worked best for his skill sets. The passive Aegis Protection is absolutely amazing and activates anytime you make 4 attacks (combination or abilities and normal attacks). If one is trying to "tank" mobs or towers, attack speed is a great way to keep yourself alive. The way I have setup my character is for higher damage output though, that way you don't have to survive long, you just blow them up before they can blink. A little rundown of my setup follows.

Summoner Spells

1. I use Heal because there are so many times that those pesky casters root you and try and burst you down, as long as you can outlast the stun you can (sometimes) get away.

2. I like exhaust a lot because of being a melee class. If your target can't run away, then they are just a wounded gazelle.

(Alternate choices)

1. If you get caught up in the blood lust, like so many of us do, then Ghost is extremely helpful to get the hell out of dodge. If this is the route you go then putting a point into Haste is a good choice just to give yourself that extra leg up.

2. If you want to get into the fray quickly you can either use (waste) Grand Skyfall or use teleport. I usually dont worry about the time it takes me, so its personal preference again depending on how you like to play.

Skill Rank Order

I start with Spear Shot, nice to start the round by taking pot shots at the enemy champions when they run too close.
Next I train up Aegis of Zeonia, this ability can help you and your team make short work of enemy champions.
Then I train Heartseeker Strike, starting out this ability is pretty weak and the cooldown and mana cost make it kind of useless, but its passive ability makes you crit on every attack on any enemy below 15% health.
I try and get a few ranks of Aegis of Zeonia because as you rank up your cooldown decreases and mana stays the same, and it is always nice to have a stun to help gank the other team.
At each level possible i train up Grand Skyfall. At first I thought this was the most ridiculous ultimate because of the long charge and notifying the enemy team that your about to land on their heads. However, used in conjuction with team stuns, catching them off guard when attacking your buildings, or just porting around the map for giggles, it can be extremely useful. On top of that, even if the enemy doesn't take the brunt of the damage, if they are caught in the AoE they become slowed, allowing for further ganking.
I never follow the same Skill Rank Order, I adapt to my situation, I suggest you do the same.

Masteries

As I said above, I'm all about blowing people (or things) up fast with high damage attacks. This leads me to the 22 points in the Offense tree. All of the stat upgrades in this tree I have selected are all to help you to have the highest damage output possible while having a couple of points in Defense and Utility to help with survivability and staying in the fray.

Runes

Armor Penetration and Critical Hit damage go hand in hand. Same theme as above, melt faces. The Attack Speed Quintessence is something I'm still toying with, as I am debating whether or not to use more Armor Penetration. I understand it is out of character for me to use attack speed, but I look at it like this: You have 17.64% Armor Penetration with the Greater Mark of Desolation x9 and 12.06% Critical Hit Damage with the Greater Seal of Furor x9 and the Greater Glyph of Furor x9. With the Greater Quintessence of Desolation x3 you would raise your Armor Penetration to 29.37% Armor Penetration. That is awesome but there can be overkill. Instead you could boost your Attack Speed with Greater Quintessence of Alacrity x3 to bring it up to 10.20% Attack Speed which will allow you to get in more hits that are still just as devastating.

Items

I will start by giving credit to DoctorLock, I was using his item progression and found it to be the most helpful and effective in games. Here is an explanation of the items and why:

1.Doran's Blade: This is a great starting item, giving you that extra health to survive in the lanes, the damage to give you the edge on your opponent, and the life steal to keep you alive if you get too cocky.

2.Chalice of Harmony: The chalice is extremely helpful, keeping your mana up so you can constantly harass enemy champions with your abilities, or allowing you to get the Spear Shot in on the minions to get the gold for the kill! Overall though it helps to have the mana regen for prolonged fights and time away from your base.

3.Zeal: Another out of character item, but it gives a helpful boost of attacking stats and a little run speed.

4.The Brutalizer: The first real damage item you will get, it helps in multiple ways. Gives you the 25 Damage boost, reduces your Ability Cooldowns 10%, and gives you... 15 Armor Penetration! Leave this as The Brutalizer until later, you need to save your money for better items at this point.

5.The Bloodthirster: When I am close to having the money for this item, I sell off my Doran's Blade as you will most likely want the space and will get plenty of damage and life steal from this item. This item has all around good damage and life steal, and if your making kills on champions it really boosts your stats!

Depending on how long your game is going to last or how desperate you are for items.

5b.(Optional)Last Whisper: This item is a great boost to your attack speed along with a little damage. It does give you a great boost to your Armor Penetration. This optional item is a great boost, but I personally would hold out for Infinity Edge, assuming you have the means to make the money.

5c.(Optional)Youmuu's Ghostblade: This is what you can upgrade The Brutalizer into. It has good damage, critical hit, armor penetration, and ability cooldown reduction, as well as an activate ability that can get you out of a tight spot. Again, I personally would be working towards Infinity Edge, but again it all depends on your cash flow and time left in game.

6.Infinity Edge: Infinity Edge is hands down the best damage weapon for you to have, its just extremely expensive. The best part of this weapon is the increased Critical Hit Damage, increasing the damage from 200% to 250%. Can you say insta-death? I have found that it is really difficult to work this weapon up in most games because of how fast the game can end. If i see the game waning then i look instead at getting The Black Cleaver